Switchable Single-Walled Carbon Nanotube-Polymer Composites for CO₂ Sensing

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensors

Background:

• Development of selective and sensitive gas sensors is crucial for environmental monitoring and industrial applications.
• Single-walled carbon nanotubes (SWCNTs) offer excellent electrical properties for sensor development but require functionalization for specific analyte interactions.
• CO2 detection is vital for climate change studies, industrial process control, and medical diagnostics.

Purpose of the Study:

• To develop a chemiresistive CO2 sensor using SWCNTs functionalized with a CO2-switchable polymer.
• To investigate the mechanism of CO2-induced conductance change in the functionalized SWCNT system.
• To evaluate the sensor's selectivity and reversibility for CO2 detection.

Main Methods:

• Synthesis of a precursor copolymer, P(4VP-VBAz), with 4-vinylpyridine (4VP) for SWCNT dispersion and azide groups for subsequent functionalization.
• Fabrication of a robust polymer-SWCNT composite film via spray coating and covalent immobilization onto a functionalized glass substrate.
• Surface functionalization with amidine groups and subsequent transformation into CO2-switchable amidinium bicarbonates via click chemistry.

Main Results:

• The CO2-switchable polymer-SWCNT composite exhibits reversible changes in electrical conductance upon exposure to CO2 under humid conditions.
• The mechanism involves the formation of amidinium bicarbonates, which increase carrier concentration or liberate holes in SWCNTs, enhancing conductance.
• The sensor demonstrates high selectivity for CO2 over other atmospheric gases like O2 and Ar.

Conclusions:

• The developed chemiresistive sensor based on functionalized SWCNTs offers a promising approach for selective and reversible CO2 detection.
• The CO2-switchable polymer strategy effectively modulates the electrical properties of SWCNTs in response to CO2.
• This technology has potential applications in environmental monitoring and industrial gas sensing.